1. Field of the Invention
The present invention relates to the use of gene activity markers for the classification of patients suffering from infectious and non-infectious multiple organ failure, respectively.
The invention further relates to the use of said gene activity classificators as stored value parameters in devices used for in vitro diagnosis for patients with infectious and non-infectious multiple organ failure. Furthermore, the invention relates to a device for in vitro diagnosis of patients suffering from infectious multiple organ failure and non-infectious multiple organ failure, respectively.
Further, the invention relates to the use of gene activity marker/classificators for the classification of gene expression profiles of patients for assessing the therapeutic effects of active substances for the treatment of infectious multiple organ failure and non-infectious multiple organ failure, respectively.
2. Description of the Related Art
Despite advances in pathophysiological understanding and the supportive treatment, the multiple organ failure syndrome (MOFS) and multiple organ failure (MOF), respectively, is the most frequent cause of death in patients in intensive care and is continuously increasing worldwide. The consequences of this development are not only considerable to the individual patient but they also have enormous effects on the costs of the public health care systems and the medical progress in many fields of medicine.
Multiple organ failure is defined as the failure of two or more vital organ systems occurring simultaneously or within a short time period. The multiple organ failure syndrome (MOFS) precedes the MOF as initial organ insufficiency [1]. Today's definition of multiple organ failure is the dysfunction of two or more organs occurring simultaneously or within a short period of time, whereas a chronically persistent organ failure can be ruled out [2]. The prognosis of MOF is closely related to the number of the involved organ systems. If one organ fails, the mortality rate within 24 hours is 22%; after 7 days it is 41%. In the case of failure of three organ systems, the mortality increases on the first day to 80% and after 4 days to 100% [3].
For the clinical scoring of the degree of severity in MOFS and MOF, the multiple organ failure score (MOF-score) of GORIS et al. [4] or, alternatively, the sepsis related organ failure assessment (SOFA) score are routinely used [5]. The MOF score renders a quick and clinically simple classification of the organ function in three grades possible. In the clinical literature, a MOF score>4 is routinely described as MOF [6]. SOFA score is a point system quickly scoring the clinical assessment of the function, of the following organ systems: respiration (lung), coagulation, liver, cardiovascular system, central nervous system and kidney. Four grades are used in this scoring system.
Clinically, the MOF runs in three stages [7]:
1. Organ in shock: The triggering pathophysiological mechanism is a perfusion deficiency of very different genesis. This happens within hours and does not yet lead to permanent damages.
2. Organ dysfunction: If the persistent perfusion deficit persists for the next few days, this will lead to the development of SIRS (Systemic inflammatory Response Syndrome, classified according to [8]) with local oedema and cell damages. This stage is called multiple organ dysfunction syndrome (MODS).3. Organ failure: The persistent perfusion deficit leads to stasis in the splanchnic area which leads to a superinfection and translocation of endotoxines from the intestines. This leads to a potentiation of the clinical symptoms and to the complete picture of the sepsis. The organ dysfunction becomes an organ failure.
MODS and MOF are clinical pictures with a complex pathophysiology. The exact molecular causes for the development and the complexity of the immunological-inflammatory host response to severe infection and trauma that can trigger SIRS and the corresponding cardiocirculatory effects are not completely understood up to the present day [9].
MODS and MOF can be both of infectiologic and non-infectiologic genesis. MODS and MOF routinely develop as a clinical important complication in patients with sepsis, after a shock that was caused by trauma, with patients after surgeries where the heart-lung machine was used, after organ transplantation, and others (FIG. 1). An important pathogenetic mechanism for the development of MODS and MOF is the development of a systemic inflammatory syndrome (SIRS, [8]). The pathophysiological processes initiated in the framework of SIRS do not only involve all components of the immune system, but interfere with all levels of the cardiocirculatory system and are not restricted to myocardial depression and vasodilation. The cardiocirculatory changes in particular on the microcirculation level form the common final distance and result in a tissue hypoxia which is considered an important cofactor in the pathogenesis of multiple organ failure.
FIG. 1 shows an exemplary description of the most important mechanisms of the development of MODS and MOF by today's standards [10]: It seems that an overactive immune system plays a decisive role in the development of multiple organ failure. In this context, the endothelium plays a central key role by secretion of cytokines and by imparting leukocyte adhesion. Signal transduction cascades are activated in the endothelial cells leading to the expression and activation of transcription factors.
The reason why there is still no sensitive/specific diagnostic being able to differentiate between infectious and non-infectious causes is the still incomplete knowledge of the early stage processes in MODS and MOF. New types of biomarkers and diagnostics, now even on a gene expression level, may provide the essential diagnostic information for early diagnosis of multiple organ failure as well as for the differentiation between infectious and non-infectious causes of MODS and MOF. Additionally, they are important in contributing to the clarification of the pathophysiologic mechanisms of systemic inflammations.
The precursory symptoms that are often used in clinical practice, as fever, leukocytosis, tachycardia and tachypnea are completely unspecific for the diagnosis of MODS or MOF as well as for differentiating between infectious and non-infectious causes of MODS and MOF. Parameters detecting irregularities in microcirculations at an early stage, as for example changes in the pH of the intestinal mucosa [11] and lactate level in the capillary bed [12, 13], emerging of a respiratory insufficiency the cause of which is not in the lung [2], the ascent of the leukocyte elastase [14,15], the height of the neopterine level [16], the activation of polymorphnuclear leukocytes and the height of the IL-6-level [17] are suitable as early parameters for the later development of MODS and MOF only to a limited extend, but they cannot contribute to the differentiation between infectious and non-infectious causes of MODS and MOF. Thus, there is urgent need for novel diagnostic methods for improving the capacity of the person skilled in the art to differentiate at an early stage between non-infectious and infectious MODS or MOF and to make predictions on how the patient will respond to specific treatments.
However, it is exactly the differentiation between infectious and non-infectious causes of MODS and MOF which is of utmost medicinal importance, as for example antibiotics may be used more efficiently with this differentiation, this contributing to considerable cost savings as well as to the avoidance of side effects caused by the unspecific application of antibiotics. In the case of non-infectious MODS or MOF it is, moreover, possible to avoid time and people-intensive diagnostic measures that are very stressful for the patient (e.g. transport to CT/MRI) for identification of the respective site of infection, the realization of comprehensive microbiological methods (e.g. examination of blood cultures for which the patient also must deliver great amounts of blood) but also the risky exchange of all plastics material connected with the patient, such as venous catheter, etc. Vice versa the quick identification of infectious causes of MODS or MOF can ensure that these measures are taken quickly and mortality can, therefore, be reduced.
Technological advances, in particular the development of microarray technology, make it now possible for the person skilled in the art to simultaneously compare 10 000 or more genes and their gene products. The use of such microarray technologies can provide information regarding the status of health, regulatory mechanisms, biochemical interactions and signal transmitter networks. As the comprehension how an organism reacts to infections is improved this way, this should facilitate the development of enhanced modalities of detection, diagnosis and therapy of infectious disorders.
Microarrays have their origin in “Southern blotting” [19], which represented the first approach to immobilizing DNA-molecules so that it can be addressed three-dimensionally on a solid matrix. The first micro arrays consisted of DNA-fragments, frequently with unknown sequence, and were applied dotwise onto a porous membrane (normally nylon). Routinely, cDNA, genomic DNA or plasmid libraries were employed and the hybridized material was labelled with a radioactive group [20-22].
Nowadays, the use of glass as substrate and fluorescence for detection together with the development of new technologies for the synthesis and for the application of nucleic acids in very high densities makes it possible to miniaturize the nucleic acid arrays. At the same time, the experimental throughput and the information content were increased [23-25].
The first explanation for the applicability of microarray technology was obtained through clinical trials in the field of cancer research. Here, expression profiles proofed to be valuable with regard to identification of activities of individual genes or groups of genes, which correlate with certain clinical phenotypes [26]. Many samples of individuals with or without acute leukaemia or diffuse B-cell lymphoma were analyzed and gene expression labels (RNA) were found and subsequently employed for the clinically relevant classification of these types of cancer [26,27]. Golub et al. found out that an individual gene is not enough to make reliable predictions, while, however, predictions based on the change in transcription of 53 genes (selected from more than 6000 genes, which were present on the arrays) are highly accurate [26].
It is known from WO 03/002763 that determination of gene expression profiles using microarrays basically can be used for the diagnosis of sepsis and sepsis-like conditions.
The Applicant's German Patent Applications DE 103 40 395.7, DE 103 36 511.7, DE 103 150 31.5 and 10 2004 009 952.9 describe that gene expression profiles, which are for example obtainable by means of the microarray technology, are, in principle, usable for the diagnosis of SIRS, generalized inflammatory inflammations, sepsis and severe sepsis. These applications are herein incorporated by reference.
It is known from Feezor et al. [28] that the gene activities of patients which developed SIRS with multiple organ dysfunction syndrome (MODS) as a consequence of their surgical treatment differ from those of patients who developed SIRS without MODS as a consequence of the same surgical treatment. However, these studies do not allow a statement on the differentiation of non-infectious MOF compared to infectious MOF, as no infection was detected in these patients.
For the classification of gene expression profiles, various methods and their use for gene expression data, for example linear and quadratic discrimination analyses, Compound Covariant Predictor, Nearest Neighbor Classification, Classification Trees or Support Vector Machines have already been described [26, 29, 30, 31, 32]. A general survey on the use of classification methods for the analysis of gene expression data is shown in [33].
It is the object of the classification methods to develop multivariant classificators which allow predictions on whether a new data set belongs to a class. Thus, patients may, for example, be classified by means of classificators into responders or non-responders regarding their response to a special treatment.
Generally, classificators are developed in three steps:
1. Selection of statistically relevant features from a large data set. For gene expression analyses, univariant tests are used as a first step to select the statistically relevant genes from various classes, based on their expression pattern.
2. Determination of the classificators by means of different classification methods, at the end of which a training set of classificators is provided.
3. Validation of this training set by means of new, non-classified test sets of gene expression profiles, and optimization of the training set.
WO 2004/108957 generally describes the classification of biomarkers (nucleic acids) and their use for the diagnosis of SIRS and sepsis, respectively. The classification and/or use of biomarkers for the diagnosis of infectious and non-infectious multiple organ failure, respectively, is not described.
The prior German Patent Application No. 102004 049897.041 describes for the first time gene activity markers for differentiating between infectious and non-infectious multiple organ failure. This application describes the use of 1297 different genes for in vitro diagnosis of patients suffering from infectious and non-infectious multiple organ failure, respectively.